Understanding EPC Calculations Mark Sreeves and Lisa Dores Who are National Energy Services?
Established 1990 Based in Milton Keynes
Own and operate NHER and SAVA Co-developed RDSAP One of the first Accreditation Schemes for Domestic Energy Assessors Presentation Overview Background
EPBD requirements for dwellings SAP scale, 2001 and 2005 RDSAP development Sensitivities
Case Study DEA process in example property EPC Online Relevant RDSAP conventions RDSAP Methodology Energy Performance of Buildings
Directive (EPBD) requirements Existing approaches & the need for a faster SAP Developing the dataset and methodology EPBD January 2003 Article 1, overall objective to reduce
energy consumption Article 3, appropriate energy calculation methodology Article 7, energy performance certificates Article 10, independent experts Article 15, transposition into law
EPBD Summary Energy Performance Certificate (EPC) Energy assessment methodology
Independent energy experts Delivery legislation RDSAP Methodology Energy Performance of Buildings Directive (EPBD) requirements Existing approaches & the need for a faster SAP
Standard Assessment Procedure For any given dwelling : An estimate of the energy costs for space heating, hot water and lighting Utilising : Standard occupancy criteria Standard weather conditions, geographical location and other geographical factors.
The SAP Scale SAP 2001 - SAP 2005 160 140 S AP
120 100 80 60 40 20 0
-2 -1 SAP 2001 SAP 2005 0 1
2 3 4 5
6 ECF (/m2/year) 7 8
9 10 Why Not Use Full SAP ? Full SAP requires full dataset Large number of data items Some items only available through new
build design process Inferences and assumptions required for existing dwellings Using Existing SAP Methods Different systems in existence : NHER, Elmhurst & MVM systems Other software providers Stock profiling systems
Directive requires a common approach to this process Common Approach: Other Reasons Comparison: Consumers to compare and assess energy performance of the building
Encouragement: Promote the improvement of the energy performance of the building User confidence: Surveyors - dont want complaints from customers Government - legal requirement, dont want
criticism RDSAP Methodology Energy Performance of Buildings Directive (EPBD) requirements Existing approaches & the need for a faster SAP Developing the dataset and
methodology RDSAP Development NHER, Elmhurst & MVM were commissioned in 2002 :
Phase 1 Data set, inferences, approach Phase 2 Testing Phase 3 Revisions Phase 4 Energy Report Phase 5 Quality Assurance
Phase 6 Field Trials Initial Dataset Criteria Accuracy Repeatability Length of survey/time
Existing Methodologies Elmhurst, MVM and NES systems differed in a number of areas Initial dataset contained the best features of each Dataset not influenced by commercial constraints
Sensitivity Testing Full SAP data items examined for sensitivity Comparison between full SAP and initial dataset Initial dataset reassessed Inferred or actual data ? - Sensitivity plus surveyor accuracy
Assumptions, inferences and surveyed items defined Sensitivity Examples (1) Number of external doors : High data variation little variation in result Number of doors can be assumed Based on dwelling type etc.
Room Height : Potential large variations in SAP 2.4 m 2.2 m = 2 SAP points Need to measure room height Relatively easy ! Sensitivity Examples (2) Window area : Potential large variations in area Time consuming to measure
Potential surveyor errors Best approach to use set of equations based on age and built form 25% in window area = 1 SAP point Non Standard Dwellings Non standard accurate rating only requires extra data collection
Excess glazing, more than one extension Excluded accurate rating cannot be provided due to limitations of the SAP model HMOs, sheltered housing Field Trials
Dataset consolidation Repeatability Accuracy Time requirements Dataset finalised Field Trials (1)
Field Trials (2) Field Trials (3) Field Trials - Conclusions Greater consistency achieved with simpler properties Larger/more complex properties showed
greatest variation Definite identifiable need for clear conventions and good training Assisted in refining the RDSAP methodology RDSAP Methodology Energy Performance of Buildings
Directive (EPBD) requirements Existing approaches & the need for a faster SAP Developing the dataset and methodology Current status EPC Assessment
Must be undertaken by Domestic Energy Assessors (DEAs) or Home Inspectors (HIs) DEA qualification is a Level 3 Diploma, HI qualification is a Level 4 Diploma All must belong to Accreditation or Certification Scheme DEA/HIs will be able to work in rental
sector social housing etc. EPC Online Case Study EPC Online - General EPC Online - Construction
Final EPC Page 1 Final EPC Page 2 Final EPC Page 3 Final EPC Page 4
Final EPC Page 5 Final EPC Page 6 Final EPC Page 7 Current Status (England & Wales )
1 August 2007 EPCs required for the marketed sales of existing dwellings with >=4 bedrooms. For newbuild, Interim and Predicted Energy Assessments. 1 October 2007 EPCs required on construction of all new dwellings 6 April 2008 EPCs required for sale/rent of nondwellings of over 500 sqm and EPCs required for the construction of all non-dwellings and 'Display EPCs'
required for public buildings of over 1,000 sqm 1 October 2008 EPCs required for rental of all dwellings and all remaining sales. EPCs required for the construction, rental or sale of all other nondwellings. NHER Web Links and Contact Details www.nher.co.uk
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